Metal complex and method for producing hydrogen peroxide

ABSTRACT

An object of the present invention is to provide a novel method for producing hydrogen peroxide by direct synthesis that is capable of taking the place of the conventional anthraquinone process, and to provide a catalyst used in the production method. 
     The present invention is a metal complex represented by the following general formula (1), (2), (3) or (4).

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a 35 U.S.C. §371 national stage patentapplication of International patent application PCT/JP2013/071015, filedon Aug. 2, 2013, published as WO/2014/045732 on Mar. 27, 2014, the textof which is incorporated by reference, and claims the benefit of thefiling date of Japanese application no. 2012-205229, filed on Sep. 19,2012, the text of which is also incorporated by reference.

TECHNICAL FIELD

The present invention relates to a metal complex that is useful as acatalyst for direct synthesis of hydrogen peroxide and a method forproducing hydrogen peroxide that uses that metal complex. The metalcomplex enables stepwise control of the reactions at each stage, from areaction that extracts electrons from hydrogen to the formation ofhydrogen peroxide, by functioning as a catalyst of a homogeneous system.

BACKGROUND ART

Hydrogen peroxide has an oxidizing power such that it exhibits strongbleaching and germicidal actions. Therefore, hydrogen peroxide isutilized as a bleaching agent for, for example, paper, pulp, and fibers,or as a germicide. Further, hydrogen peroxide is an important industrialproduct widely used in oxidation reactions including epoxidation andhydroxylation.

Further, hydrogen peroxide is used in the semiconductor industry,specifically used in, for example, cleaning of the surfaces ofsemiconductor substrates and the like, chemical polishing of thesurfaces of copper, tin, and other copper alloys, and etching forelectronic circuit. Hydrogen peroxide produces only water and oxygen asdecomposition products, and hence is considered important from theviewpoint of green chemistry, and has attracted attention as asubstitute material for a chlorine bleaching agent.

Although hydrogen peroxide is currently synthesized industrially by ananthraquinone process, since this process consumes a large amount ofenergy, there is a need to develop a new synthesis method.

As one alternative method, there has been considerable activity in thedevelopment of a method for synthesizing hydrogen peroxide directly fromhydrogen and oxygen. Non-homogeneous solid catalysts have typically beendeveloped for use as catalysts of this direct synthesis method, andvarious non-homogeneous solid catalysts have been reported. For example,Patent Document 1 and Non-Patent Document 1 disclose that hydrogenperoxide is synthesized directly from hydrogen and oxygen using an alloysolid catalyst such as platinum-palladium.

In addition, organometallic complexes, in which various ligands are usedfor the metal elements such as members of the platinum group or irongroup, have also been proposed for use as catalysts for direct synthesisof hydrogen peroxide (Patent Documents 2 and 3).

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: Japanese Examined Patent Publication No.    S40-19006-   Patent Document 2: Japanese Examined Patent Publication No. S57-246-   Patent Document 3: Japanese Laid Open Patent Publication (kohyo) No.    2009-530503

Non-Patent Documents

-   Non-Patent Document 1: Edwards, J. K., et al., Science, Vol. 323, p.    1037, 2009

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

An object of the present invention is to provide a novel method forproducing hydrogen peroxide by direct synthesis that is capable oftaking the place of the conventional anthraquinone process, and toprovide a catalyst used in the production method.

Means for Solving the Problems

As a result of conducting extensive studies in consideration of theaforementioned problems, the inventors of the present invention havefound that a metal complex represented by the general formula (1) belowreturns to the metal complex of general formula (1) after going throughthe stepwise formation of metal complexes represented by the generalformulas (2) to (4) below by introducing hydrogen and oxygen, that theextraction of electrons from hydrogen, the donation of electrons tooxygen, and the formation of hydrogen peroxide occur, and that thesereactions can be easily controlled in a stepwise manner, thereby leadingto completion of the present invention.

Namely, the present invention is as described below.

[1] A metal complex represented by the following general formula (1),(2), (3) or (4):

[wherein, M represents chromium, manganese, iron, cobalt, nickel,copper, molybdenum, ruthenium, rhodium, palladium, silver, tungsten,rhenium, osmium, iridium, platinum or gold, n+ represents the charge ofM, R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ each independently represent ahydrogen atom, halogen, hydroxyl group, alkyl group having 1 to 20carbon atoms, aralkyl group having 7 to 20 carbon atoms, aryl grouphaving 6 to 20 carbon atoms, silyl group substituted with a hydrocarbongroup having 1 to 20 carbon atoms, alkoxy group having 1 to 20 carbonatoms, aralkyloxy group having 7 to 20 carbon atoms, aryloxy grouphaving 6 to 20 carbon atoms or amino group substituted with ahydrocarbon group having 1 to 20 carbon atoms, X, Y and Z eachindependently represent H₂O, OH⁻, O²⁻ or a halogen ion, m+ representsthe charge of the moiety of the metal complex excluding An1, An1represents a counter ion that neutralizes the charge of the moiety ofthe metal complex excluding An1, m− represents the charge of An1, andthe alkyl group, aralkyl group, aryl group, silyl group, alkoxy group,aralkyloxy group, aryloxy group and amino group may be substituted witha hydroxyalkoxyalkoxy group];

[wherein, M, n, R¹ to R⁹ and Y are the same as defined in formula (1),1+ represents the charge of the moiety of the metal complex excludingAn2, An2 represents a counter ion that neutralizes the charge of themoiety of the metal complex excluding An2, and 1-represents the chargeof An2];

[wherein, M, n, R¹ to R⁹ and Y are the same as defined in formula (1),k+ represents the charge of the moiety of the metal complex excludingAn3, An3 represents a counter ion that neutralizes the charge of themoiety of the metal complex excluding An3, k− represents the charge ofAn3, and two each of the M, n, R¹ to R⁹ and Y may each be the same ordifferent]; and,

[wherein, M, n, R¹ to R⁹, X and Y are the same as defined in formula(1), p+ represents the charge of the moiety of the metal complexexcluding An4, An4 represents a counter ion that neutralizes the chargeof the moiety of the metal complex excluding An4, p− represents thecharge of An4, and two each of the M, n, R¹ to R⁹, X and Y may each bethe same or different].

[2] The metal complex described in [1], wherein the number of carbonatoms of the alkyl group is 1 to 4, the number of carbon atoms of thearalkyl group is 7 to 10, the number of carbon atoms of the aryl groupis 6 to 9, the number of carbon atoms of the alkoxy group is 1 to 4, thenumber of carbon atoms of the aralkyloxy group is 7 to 10, and thenumber of carbon atoms of the aryloxy group is 6 to 9.

[3] The metal complex described in [1] or [2], wherein, in generalformula (1), R¹, R², R⁴, R⁵, R⁶, R⁸ and R⁹ represent hydrogen atoms, R³and R⁷ represent methyl groups, one of X, Y and Z represents OH⁻, theremaining two represent H₂O, and An1 represents a nitrate ion.

[4] The metal complex described in [1] or [2], wherein, in generalformula (2), R¹, R², R⁴, R⁵, R⁶, R⁸ and R⁹ represent hydrogen atoms, R³and R⁷ represent methyl groups, Y represents H₂O and An2 represents anitrate ion.

[5] The metal complex described in [1] or [2], wherein, in generalformula (3), R¹, R², R⁴, R⁵, R⁶, R⁸ and R⁹ represent hydrogen atoms, R³and R⁷ represent methyl groups, Y represents H₂O and An3 represents anitrate ion.

[6] The metal complex described in [1] or [2], wherein, in generalformula (4), R¹, R², R⁴, R⁵, R⁶, R⁸ and R⁹ represent hydrogen atoms, R³and R⁷ represent methyl groups, X and Y represent H₂O and An4 representsa nitrate ion.

[7] A method for producing hydrogen peroxide comprising the formation ofhydrogen peroxide from hydrogen and oxygen in the presence of a metalcomplex represented by the following general formula (1):

[wherein, M represents chromium, manganese, iron, cobalt, nickel,copper, molybdenum, ruthenium, rhodium, palladium, silver, tungsten,rhenium, osmium, iridium, platinum or gold, n+ represents the charge ofM, R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ each independently represent ahydrogen atom, halogen, hydroxyl group, alkyl group having 1 to 20carbon atoms, aralkyl group having 7 to 20 carbon atoms, aryl grouphaving 6 to 20 carbon atoms, silyl group substituted with a hydrocarbongroup having 1 to 20 carbon atoms, alkoxy group having 1 to 20 carbonatoms, aralkyloxy group having 7 to 20 carbon atoms, aryloxy grouphaving 6 to 20 carbon atoms or amino group substituted with ahydrocarbon group having 1 to 20 carbon atoms, X, Y and Z eachindependently represent H₂O, OH⁻, O²⁻ or a halogen ion, m+ representsthe charge of the moiety of the metal complex excluding An1, An1represents a counter ion that neutralizes the charge of the moiety ofthe metal complex excluding An1, m− represents the charge of An1, andthe alkyl group, aralkyl group, aryl group, silyl group, alkoxy group,aralkyloxy group, aryloxy group and amino group may be substituted witha hydroxyalkoxyalkoxy group].

Effects of the Invention

According to the present invention, a novel method for producinghydrogen peroxide by direct synthesis and a catalyst used in theproduction method are provided. In this production method, each reactionfrom the extraction of electrons from hydrogen to the formation ofhydrogen peroxide can be easily controlled in a stepwise manner.

MODE FOR CARRYING OUT THE INVENTION

The following provides a detailed explanation of the present invention.

[Metal Complex]

The metal complex of the present invention is represented by thefollowing general formula (1).

<M and n+>

In general formula (1), M represents chromium, manganese, iron, cobalt,nickel, copper, molybdenum, ruthenium, rhodium, palladium, silver,tungsten, rhenium, osmium, iridium, platinum or gold. Any of thesemetals can adopt any of the coordinate structures represented by generalformulas (1) to (4), and function as the central metal in the metalcomplex of the present invention. In addition, n+ represents the chargeof M and is a number within the range of +7 to 0.

M is preferably rhodium from the viewpoint of catalytic efficiency inthe case of using the metal complex of the present invention forcatalyzing the synthesis of hydrogen peroxide.

<R¹ to R⁹>

In general formula (1), R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ eachindependently represent a hydrogen atom, halogen, hydroxyl group, alkylgroup having 1 to 20 carbon atoms, aralkyl group having 7 to 20 carbonatoms, aryl group having 6 to 20 carbon atoms, silyl group substitutedwith a hydrocarbon group having 1 to 20 carbon atoms, alkoxy grouphaving 1 to 20 carbon atoms, aralkyloxy group having 7 to 20 carbonatoms, aryloxy group having 6 to 20 carbon atoms or amino groupsubstituted with a hydrocarbon group having 1 to 20 carbon atoms. Thealkyl group, aralkyl group, aryl group, silyl group, alkoxy group,aralkyloxy group, aryloxy group and amino group may be substituted witha hydroxyalkoxyalkoxy group.

Examples of the aforementioned halogen include fluorine, chlorine,bromine and iodine. Among these, chlorine is preferable.

In addition, examples of hydrocarbon groups having 1 to 20 carbon atomsthat substitute on the aforementioned silyl group include a methylgroup, ethyl group, propyl group and butyl group. Since a silyl group issubstituted with a maximum of three hydrocarbon groups, the maximumnumber of carbon atoms in a single hydrocarbon group-substituted silylgroup is 60.

Examples of hydrocarbon groups having 1 to 20 carbon atoms thatsubstitute on the aforementioned amino group are the same as thehydrocarbon groups that substitute on the aforementioned silyl group.Since an amino group is substituted with a maximum of two hydrocarbongroups, the maximum number of carbon atoms in a single hydrocarbongroup-substituted amino group is 40.

Moreover, from the viewpoints of high reactivity in the case of usingthe metal complex of the present invention for the synthesis of hydrogenperoxide and availability of raw materials used to produce theaforementioned metal complex, the number of carbon atoms of theaforementioned alkyl group is preferably 1 to 4, the number of carbonatoms of the aforementioned aralkyl group is preferably 7 to 10, thenumber of carbon atoms of the aforementioned aryl group is preferably 6to 9, the number of carbon atoms of the aforementioned alkoxy group ispreferably 1 to 4, the number of carbon atoms of the aforementionedaralkyloxy group is preferably 7 to 10, and the number of carbon atomsof the aforementioned aryloxy group is preferably 6 to 9.

Specific examples of such alkyl groups include a methyl group, ethylgroup, propyl group and butyl group.

Specific examples of aralkyl groups include a benzyl group and phenethylgroup.

Specific examples of aryl groups include a phenyl group, tolyl group,xylyl group and mesityl group.

Specific examples of alkoxy groups include an ethoxy group, methoxygroup, propoxy group and butoxy group.

Specific examples of aralkyloxy groups include a benzyloxy group andphenethyloxy group.

Specific examples of aryloxy groups include a phenyloxy group, tolyloxygroup, xylyloxy group and mesityloxy group.

R¹ to R⁹ are preferably such that R¹, R², R⁴ to R⁶, R⁸ and R⁹ arehydrogen atoms and R³ and R⁷ are hydrocarbon groups having 1 to 20carbon atoms or hydrogen atoms, and more preferably such that R¹, R², R⁴to R⁶, R⁸ and R⁹ are hydrogen atoms and R³ and R⁷ are methyl groups,from the viewpoint of high reactivity.

<X, Y and Z>

X, Y and Z in the aforementioned general formula (1) each independentlyrepresent H₂O, OH⁻, O²⁻ or a halogen ion. Examples of the halogen ioninclude a fluoride ion, chloride ion, bromide ion and iodide ion, andamong these, a chloride ion is preferable.

X, Y and Z are coordinated with the metal M together with the N atoms ontwo imidazole rings and an N atom on a pyridine ring. Furthermore, thevalence of M in general formula (1) is +3 and the metal in this formprefers hexa-coordination.

In the method for producing hydrogen peroxide of the present inventionto be subsequently described, a structure in which an imidazole ring,pyridine ring and imidazole ring are coordinated with the metal M inthis order in the metal complex of the present invention (see generalformula (1)) is an important key structure. Moreover, since this ligandstructure (key structure) is rigidly fixed by the coordination of X, Yand Z, substituents on the imidazole rings and pyridine ring have littleeffect on this key structure.

One of X, Y and Z is preferably OH⁻ and the remaining two are preferablyH₂O from the viewpoint of high reactivity. Furthermore, although whetherX, Y and Z are H₂O, OH⁻ or O²⁻ is largely dependent on the pH of thesolution obtained by dissolving the metal complex of the presentinvention in a reaction medium to be subsequently described, and on thepH of the production system at the production stage of the metal complexof the present invention, X, Y and Z are each independently selectedfrom the aforementioned H₂O, OH⁻, O²⁻ and a halogen ion in a combinationsuch that the charge of the moiety of general formula (1) excluding An1(to also be referred to as “moiety 1”) is from 0 to +3.

<m+>

In the aforementioned general formula (1), m+ represents the charge ofmoiety 1, and can adopt a charge within the range of 0 to +3 accordingto the types of X, Y and Z.

<An1 and m−>

In the aforementioned general formula (1), An1 represents a counter ionused to make the overall charge of the metal complex 0 by neutralizingthe charge of the moiety 1. The number of counter ions is the numberrequired to neutralize the charge of the moiety 1. Thus, the overallcharge of An1 is m−, and m− can adopt a charge within the range of −3 to0. Furthermore, An1 is not present in the case m+ is 0, namely in thecase m− is also 0.

Examples of the counter ion include nitrate ion,trifluoromethanesulfonate ion, sulfate ion, tetrafluoroborate ion,tetraphenylborate ion, hexafluorophosphate ion, chloride ion, bromideion and iodide ion. The counter ion is preferably a nitrate ion ortrifluoromethanesulfonate ion from the viewpoint of facilitatingproduction of the metal complex of the present invention.

<Metal Complex of Present Invention>

Preferable examples of the metal complex of the present inventioncomposed of the key structure and various substituents and the like aspreviously explained are as indicated below.

(1) Metal complex wherein, in general formula (1), R¹, R², R⁴, R⁵, R⁶,R⁸ and R⁹ represent hydrogen atoms, R³ and R⁷ represent methyl groups,one of X, Y and Z represents OH⁻, the remaining two represent H₂O, andAn1 represents a nitrate ion.

(2) Metal complex wherein, in general formula (1), R³ and R⁷independently represent a hydrogen atom or methyl group, R⁵ represents ahydrogen atom, hydroxyl group or (2-(2-(2-hydroxyethoxyl)ethoxy)ethoxygroup, and X, Y and Z each independently represent H₂O or OH⁻.

[Metal Complex Production Method]

The metal complex of the present invention as explained above can beproduced in the manner indicated below.

First, a metal M capable of adopting a hexa-coordination in generalformula (1) is provided. This is typically commercially available in theform of a halide, hydrate or oxide and the like. The metal complex ofthe present invention is obtained by mixing or heating to reflux themetal with a Compound 1, which is represented by the following formulaand serves as a ligand in the metal complex of the present invention, ina suitable solvent such as ethanol.

In the resulting metal complex of the present invention, if a halide hasbeen used for the metal M, then X, Y and Z are halogen ions orsolvent-derived ions thereof, and in the case the counter ion An1 ispresent, it is also a halogen ion or solvent-derived ion thereof.

The heating to reflux is normally carried out for 1 to 48 hours.

In addition, Compound 1 serving as the aforementioned ligand can besynthesized in accordance with the method described in R. F. Carina, G.Bernardinelli and A. F. Williams, Angew. Chem. Int. Ed., 1993, 32, 1463.

In addition, X, Y, Z and An1 can be altered by reacting an appropriatereagent and the like with the metal complex of the present inventionsynthesized in the manner described above.

For example, in the case of changing X, Y and Z to H₂O and the like, themetal complex is reacted with water. Here, as a general indicatorthereof, X, Y and Z are all H₂O within a pH range of 1 to 3.5, one of X,Y and Z is OH⁻ and the remaining two are H₂O within a pH range of 3.5 to7.8, and two or more of X, Y and Z are OH⁻ at a pH of 7.8 or higher.Moreover, one or more of X, Y and Z is O²⁻ at a pH of 12 or higher.

In the case of changing An1, for example, a reagent that provides acounter ion as previously explained (such as a nitrate ion,trifluoromethanesulfonate ion or sulfate ion) is reacted with the metalcomplex.

In the reactions for altering these X, Y, Z and An1, the reactiontemperature is normally 5° C. to 200° C., the reaction pressure isnormally 1 atm to 10 atm, and the reaction time is normally 1 hour to 48hours.

[Hydrogen Peroxide Production Method]

As is explained below, the metal complex of the present invention asexplained above can be used as a catalyst in a method for producinghydrogen peroxide by a novel mechanism.

In the method for producing hydrogen peroxide of the present invention,hydrogen peroxide is produced by going through a cycle consisting ofsequentially converting the metal complex of the present invention tocompounds represented by general formulas (2), (3) and (4) and thenreturning to the original compound represented by general formula (1) ina suitable reaction medium as explained below. The following provides anexplanation of each conversion step.

<Step 1: Metal Complex Represented by General Formula (1)→Low ValenceMetal Complex Represented by General Formula (2)>

In the method for producing hydrogen peroxide of the present invention,the metal complex of the present invention represented by generalformula (1) is first reacted with hydrogen (H₂) as indicated by thefollowing reaction formula to form a low valence metal complexrepresented by general formula (2).

As a result of this reaction, a metal M accepts two electrons from ahydrogen molecule and thereby valence decreases by two resulting in atetra-coordinated form. As a result, electrons derived from the hydrogenmolecule are retained in the metal complex.

Furthermore, in general formula (2), M, n, R¹ to R⁹ and Y are the sameas defined in formula (1), 1+ represents the charge of the moiety of themetal complex excluding An2, An2 represents a counter ion thatneutralizes the charge of the moiety, and the type, number and the likethereof are the same as An1. In addition, 1− represents the overallcharge of An2. Furthermore, the low valence metal M can have a negativecharge, and in that case, the charge 1+ of the moiety excluding An2 mayalso be negative. At that time, the counter ion An2 is a cation, andexamples thereof include a sodium ion, lithium ion andtetraphenylphosphonium ion.

<Step 2: Low Valence Metal Complex Represented by Formula (2)→BinuclearMetal Complex Represented by General Formula (3)>

Next, the low valence metal complex represented by general formula (2)is oxidized by an oxidizing agent such as oxygen (O₂) resulting in theformation of a binuclear metal complex represented by general formula(3) as indicated in the following reaction formula.

As a result, the valence of the metal M increases by one resulting in apenta-coordinated form. As a result of this reaction, half of theelectrons retained in the metal (two of the four electrons retained intwo low valence metal complexes) are incorporated in the oxidizing agentsuch as oxygen. The oxidizing agent that has incorporated the electronscouples with protons (H⁺) derived from the reaction medium or generatedin Step 1. For example, water is released if the oxidizing agent isoxygen.

Furthermore, in general formula (3), M, n, R¹ to R⁹ and Y are the sameas defined in formula (1), k+ represents the charge of the moiety of thebinuclear metal complex excluding An3, An3 represents a counter ion thatneutralizes the charge of the moiety, and the type, number and the likethereof are the same as An1. In addition, k− represents the overallcharge of An3. There are cases in which the charge k+ of the moiety ofthe binuclear metal complex excluding An3 is negative, and at that time,the counter ion An3 is a cation.

If a single compound is used for the metal complex represented bygeneral formula (1) in Step 1, the upper metal complex moiety and thelower metal complex moiety in the binuclear metal complex represented bygeneral formula (3) have the same structure. On the other hand, if amixture of a plurality of compounds is used for the metal complexrepresented by general formula (1), the upper metal complex moiety andthe lower metal complex moiety in the binuclear metal complex may bedifferent.

In oxidizing the low valence metal complex represented by generalformula (2), although known oxidizing agents such as oxygen, persulfuricacid, tert-butylhydroperoxide or iodosobenzene can be used without anyspecial restrictions, from the viewpoint of subsequently carrying outthe reaction by which the binuclear metal complex of general formula (3)is converted to a peroxo complex represented by general formula (4) inthe following Step 3 or from the viewpoint of saving the bother ofhaving to remove the oxidizing agent used in Step 2 from the reactionsystem, oxygen is preferably used as the oxidizing agent.

<Step 1 Binuclear Metal Complex Represented by General Formula(3)→Peroxo Complex Represented by General Formula (4)>

Next, following Step 2, the binuclear metal complex represented bygeneral formula (3) is reacted with oxygen (O₂) and is converted to theperoxo complex represented by general formula (4) as indicated by thefollowing reaction formula.

In this reaction, the two electrons present in the binuclear metalcomplex that were extracted from hydrogen in Step 1 are transferred fromthe metal M to oxygen and are retained in the —O—O— moiety. As a result,the valence of the metal M in the binuclear metal complex increases by 1and it returns to the hexa-coordinated form.

Furthermore, in general formula (4), M, n, R¹ to R⁹, X and Y are thesame as defined in formula (1), p+ represents the charge of the moietyof the peroxo complex excluding An4, An4 represents a counter ion thatneutralizes the charge of the moiety, and the type, number and the likethereof are the same as An1. In addition, p− represents the overallcharge of An4.

Furthermore, in the case of using a mixture of a plurality of compoundsfor the metal complex represented by general formula (1) in Step 1,there are cases in which the structure of the upper metal complex moietyand the structure of the lower metal complex moiety in the peroxocomplex may be different, as was previously described.

<Step 4: Peroxo Complex Represented by General Formula (4)→Metal ComplexRepresented by General Formula (1)>

Finally, the peroxo complex represented by general formula (4) istreated with a Lewis acid to let the complex react with protons (H⁺)derived from the acid, whereby releasing hydrogen peroxide (H₂O₂) asindicated by the following reaction formula.

Examples of the Lewis acid include hydrochloric acid, sulfuric acid,nitric acid, trifluoromethanesulfonic acid, acetic acid, formic acid andtetrafluoroboric acid.

In addition, in Step 4, the proton donor in the form of the Lewis acidis not particularly required to be newly added, but rather protonsderived from the reaction medium or residual protons generated in Step 1(two of the four H⁺ generated in association with formation of twomolecules of low valence metal complex) can be used, and doing so ispreferable from the viewpoints of cost and reaction simplicity.

The hydrogen peroxide formed is recovered after purifying by aconventionally known purification method such as extracting from atwo-phase system consisting of organic solvent and water into an aqueousphase.

<Reaction Medium>

The method for producing hydrogen peroxide of the present invention iscarried out in a suitable reaction medium. The reaction medium isnormally a liquid phase and can be used without any particularlimitations provided it does not inhibit the aforementioned reactions ofthe cycle of Steps 1 to 4 and dissolves the aforementioned metalcomplexes represented by general formulas (1) to (4). In the presentinvention, a reaction medium can be used by suitably selecting thatwhich satisfies the aforementioned conditions from among conventionallyused reaction media in the method for producing hydrogen peroxide bydirectly reacting hydrogen and oxygen.

Examples of the reaction medium include water; alcohols such as methanoland ethanol; aprotic polar solvents such as acetone, cyanomethane, DMFand DMSO; and mixed solvents thereof. Among these, water is preferable.

Moreover, these reaction media may contain an additive for adjusting pH,stabilizing effects or improving gas-solubility, and may also contain,for example, an acid such as phosphoric acid or sulfuric acid or afluorine-based inert liquid.

<Example of Cycle of Hydrogen Peroxide Production Method>

The following provides an explanation of a specific embodiment of themethod for producing hydrogen peroxide of the present invention based ona typical example of the cycle of the method for producing hydrogenperoxide of the present invention. The typical example of the cycle isas indicated below.

(Step 1)

In this cycle, the starting substance is the metal complex of thepresent invention represented by general formula (1), and this isdissolved in a suitable reaction medium. Since the metal complexfunctions as a homogeneous catalyst by dissolving in the reactionmedium, the reaction can be carried out more efficiently than withconventional non-homogeneous catalysts.

Hydrogen gas is introduced into this reaction medium solution followedby carrying out Step 1 (wherein the metal complex and hydrogen moleculesreacted in a 1:1 ratio) to cause electrons to be retained in the metalM, thereby obtaining the low valence metal complex of general formula(2). Here, unreacted hydrogen gas can be easily recovered by a suitablerecovery means such as an aspiration means and reused.

(Step 2)

Next, Step 2 is carried out by introducing oxygen gas into the reactionmedium solution of the low valence metal complex (oxidation reaction oflow valence metal complex) to obtain the binuclear metal complexrepresented by general formula (3) whereby a portion of the electronsretained in the metal M in Step 1 are transferred to oxygen and water isreleased (0.5 molecules of oxygen react with two molecules of the lowvalence metal complex). If the reaction medium is water, since it doesnot occur that the reaction medium becomes heterogeneous as a result ofthis released water to have a detrimental effect on the formationefficiency of hydrogen peroxide, water is preferable as the reactionmedium. The following explanation is based on the use of water as thereaction medium.

Although there is a risk of explosion if hydrogen (used in Step 1) andoxygen (used in Step 2) are present together, since that risk iseliminated if unreacted hydrogen gas is recovered in Step 1 aspreviously described, the method for producing hydrogen peroxide of thepresent invention is a method that is superior in terms of beingextremely safe.

In addition, in the case of conventional methods for producing hydrogenperoxide, since hydrogen gas and oxygen gas are basically introducedsimultaneously, these gases are used after being diluted with a dilutinggas such as nitrogen in order to lower the risk of explosion. Since thistype of dilution is not required in the present invention, it isadvantageous in terms of cost, and since the amounts of hydrogen andoxygen used per unit reaction volume or per unit reaction time increase,there is a potential for improving hydrogen peroxide productionefficiency.

(Step 3)

After having carried out Step 2, Step 3 is carried out by introducingoxygen gas into an aqueous solution of the binuclear metal complexrepresented by general formula (3) whereby residual electrons retainedin the metal M migrate to oxygen (the binuclear metal complex and oxygenmolecules react at a ratio of 1:1). As a result, the peroxo complexrepresented by general formula (4) is obtained.

Furthermore, this Step 3 can be carried out simultaneously with Step 2if excess oxygen gas is introduced in Step 2. After having obtained theperoxo complex in this Step 3, unreacted oxygen gas can be recoveredwith a suitable recovery means such as an aspiration means and reused.

In addition, as a result of this recovery, the occurrence of anexplosion can be avoided when Step 1 is again carried out to introducehydrogen gas after continuing with the cycle through the next Step 4.

(Step 4)

As a result of reacting protons (H+) with the peroxo complex obtained inStep 3, hydrogen peroxide is obtained from the oxygen (—O—O—) thatretained electrons in Step 3, and the metal complex represented bygeneral formula (1) is regenerated. The protons may be supplied byseparately adding a Lewis acid to the aqueous solution of the peroxocomplex, protons derived from the reaction medium can be used, orresidual protons generated in Step 1, a portion of which protons wereused in Step 2, can be used. In this example, since water is thereaction medium, protons are supplied from the water or residual protonsof Step 2 are used.

The hydrogen peroxide can be recovered with a known purification meansas previously described, and hydrogen peroxide is produced continuouslyby proceeding with the cycle. Furthermore, although unreacted oxygen gasmay be recovered in Step 3, it may also be recovered followingcompletion of Step 4 immediately prior to Step 1 in which hydrogen gasis introduced.

As has been explained above, the method for producing hydrogen peroxideof the present invention produces hydrogen peroxide by theaforementioned reaction cycle consisting of Steps 1 to 4, and thereaction of each step can be carried out in a stepwise manner.

Namely, the reaction can be stopped at the point Step 1 is carried outor can be stopped at the point Step 2 is carried out, and the metalcomplex obtained in each reaction stage can be isolated. Since each stepcan be arbitrarily controlled in a stepwise manner in this way, it iseasy to determine the current stage in the cycle, hydrogen gas or oxygengas can be suitably introduced correspondingly, and recovery of theseunreacted gases can be carried out precisely. Moreover, the reactionapparatuses can be separated for each step.

<Reaction Conditions>

Since the yield of hydrogen peroxide can be enhanced by setting thepressure to a high level (increasing the amounts of hydrogen and oxygenintroduced) in the cycle of the method for producing hydrogen peroxideof the present invention explained above, the method is normally carriedout using an autoclave or other pressure-resistant reaction apparatus.

The reaction apparatus of any type, for example, of an agitated vesseltype, a bubble column type, a fixed bed type, or a microreactor type canbe used as the reaction apparatus, and the reaction can be conductedeither in a batchwise manner or in a continuous manner. The reactionapparatus has a gas introducing portion and a gas discharging portion(utilized for, e.g., recovery of unreacted hydrogen gas and unreactedoxygen gas), and further normally has, a thermometer and a pressuregauge, etc.

The reaction temperature during the cycle for synthesizing hydrogenperoxide in the present invention is preferably −80° C. to 100° C. andmore preferably 10° C. to 30° C. Although there are no particularlimitations on the reaction pressure, it is preferably 0.01 atm to 100atm and more preferably 1 atm to 10 atm. In addition, the reaction timeis normally 0.1 hour to 200 hours and preferably 1 hour to 50 hours.

In addition, although it is preferred that unreacted hydrogen gas isrecovered following the introduction of hydrogen gas in Step 1 toprevent the occurrence of an explosion following subsequent introductionof oxygen gas in the present invention, as was previously described,hydrogen gas and oxygen gas may also be introduced simultaneously.

In this case, hydrogen peroxide is produced continuously by continuingto proceed through the aforementioned cycle without stopping at eachstage. The flow rates of hydrogen gas and oxygen gas at this time arepreferably such that the ratio thereof is that oxygen is in excessrelative to hydrogen while avoiding the explosive range (such a ratiothat the volumetric ratio of the flow rate of hydrogen gas to oxygen gasis within the range of 1:2 to 1:10). Moreover, from the viewpoint ofsafety, the hydrogen gas and oxygen gas are preferably diluted with aninert gas such as nitrogen gas in order to further lower the risk ofexplosion.

In addition, these gases are normally introduced into the liquid phase,or in other words, are introduced into the reaction medium solution fromthe viewpoint of reaction efficiency.

EXAMPLES

Although the following provides a more detailed explanation of thepresent invention through Examples, the present invention is not limitedto them.

Example 1 Synthesis of [Rh^(III)(iMP)Cl₃]

Rh^(III)Cl₃.3H₂O (2.0 mmol) and iMP (2.1 mmol)(iMP=2,6-bis(1-methyl-1H-imidazol-2-yl)pyridine) were heated to refluxfor 12 hours in ethanol to obtain [Rh^(III)(iMP)Cl₃] (a compound ofgeneral formula (1) in which M is Rh, R¹, R², R⁴, R⁵, R⁶, R⁸ and R⁹ arehydrogen atoms, R³ and R⁷ are methyl groups, and X, Y and Z are chlorideions) (Rh^(III)Cl₃.3H₂O is a commercially available product (rhodiumtrichloride trihydrate), and iMP was synthesized with reference to R. F.Carina, G. Bernardinelli and A. F. Williams, Angew. Chem. Int. Ed.,1993, 32, 1463).

Elementary analysis: theoretical values ([Rh^(III)(iMP)Cl₃]); C, 34.81%;H, 2.92%; N, 15.61%; measured values; C, 34.68%; H, 2.78%; N, 15.55%.

Example 2 Synthesis of [Rh^(III)(iMP)(OH)(H₂O)₂](NO₃)₂ {[1](NO₃)₂}

AgNO₃ (3.69 mmol) was added to the [Rh^(III)(iMP)Cl₃] (1.23 mmol)obtained in Example 1 in water followed by refluxing for 12 hours at100° C. to precipitate AgCl. When AgCl was removed by filtering thereaction solution followed by removing the water from the filtrate underreduced pressure, yellow powders were obtained. The yellow powders werethen recrystallized using methanol to obtain yellow crystals.

Elementary analysis: theoretical values ([1](NO₃)₂); C, 35.10%; H,3.14%; N, 13.65%; measured values; C, 34.92%; H, 3.12%; N, 13.61%.

Example 3 Synthesis of [Rh^(I)(iMP)(H₂O)](NO₃) {[2](NO₃)} (Step 1)

The pH of an aqueous solution of [1](NO₃)₂ (0.92 mmol) obtained inExample 2 was adjusted to pH 6 using a 0.01 M aqueous nitric acidsolution followed by introducing hydrogen (1 atm) into the aqueoussolution at 25° C., allowing to react and gradually allowing a deepgreen solid to precipitate over the course of 24 hours. This precipitatewas filtered and dried under reduced pressure to obtain a deep greensolid.

Elementary analysis: theoretical values ([2](NO₃)); C, 43.29%; H, 3.15%;N, 13.46%; measured values; C, 43.40%; H, 3.25%; N, 13.63%.

Example 4 Synthesis of [Rh^(II) ₂(iMP)₂(H₂O)₄](NO₃)₄.H₂O {[3](NO₃)₄.H₂O}(Step 2)

Sodium nitrate (0.25 mmol) was added to the [2](NO₃) (0.24 mmol)obtained in Example 3 followed by introducing oxygen (1 atm) into thissuspended aqueous solution for 3 hours at 25° C. to obtain a redsolution. The resulting solution was passed through Sephadex followed byremoving the solvent under reduced pressure to obtain a red solid.

Elementary analysis: theoretical values ([3](NO₃)₄H₂O); C, 34.57%; H,3.09%; N, 13.44%; measured values; C, 34.66%; H, 2.92%; N, 13.46%.

Example 5 Synthesis of [Rh^(III) ₂(iMP)₂(H₂O)₄(μ-η¹:η¹-O₂)](NO₃)₄{[4](NO₃)₄} (Step 3)

Oxygen (1 atm) was passed through an aqueous solution of the{[3](NO₃)₄.H₂O} (0.10 mmol) obtained in Example 4 for 3 hours at 25° C.after which the solution changed to a reddish-brown solution. Thesolvent was removed under reduced pressure to obtain a reddish-brownsolid.

Elementary analysis: theoretical values ([4](NO₃)₄); C, 30.13%; H,3.31%; N, 18.92%; measured values; C, 30.23%; H, 3.11%; N, 1.8.77%.

Example 6 Release of Hydrogen Peroxide (Step 4) and Detection

Nitric acid was added to an aqueous solution of the [4](NO₃)₄ (0.13mmol) obtained in Example 5 at 25° C. followed by reacting for 3 hoursand releasing hydrogen peroxide. Quantitative determination was carriedout using a titanium complex and the yield of hydrogen peroxide was 3%based on the [4](NO₃)₄ obtained in Step 3 carried out immediately priorthereto (the method used to quantify hydrogen peroxide was the samemethod as that described in W. C. Wolfe, Anal. Chem. 1962, 34, 1328).Hydrogen peroxide yield was determined using the same standard in thefollowing examples as well.

Example 7 Synthesis of [Cr^(III)(iMP)Cl₃]

Cr^(III)Cl₃ (2.0 mmol) and iMP (2.1 mmol) were mixed in ethanol toobtain [Cr^(III)(iMP)Cl₃] (Cr^(III)Cl₃ is a commercially availableproduct (chromium trichloride)).

Elementary analysis: theoretical values ([Cr^(III)(iMP)Cl₃]); C, 39.27%;H, 3.30%; N, 17.61%; measured values; C, 39.53%; H, 3.51%; N, 17.39%.

Example 8 Synthesis of [Cr^(III)(iMP)(OH)(H₂O)₂](NO₃)₂ {[5](NO₃)₂}

AgNO₃ (3.0 mmol) was added to the [Cr^(III)(iMP)Cl₃] (1.0 mmol) obtainedin Example 7 in water (temperature: 25° C.) followed by precipitation ofAgCl. When AgCl was removed by filtering the reaction solution followedby removing the water from the filtrate under reduced pressure, yellowpowders were obtained. The yellow powders were then recrystallized usingmethanol to obtain yellow crystals.

Elementary analysis: theoretical values ([5](NO₃)₂); C, 33.34%; H,3.87%; N, 20.94%; measured values; C, 33.30%; H, 3.78%; N, 20.83%.

Example 9 Synthesis of [Cr^(I)(iMP)(H₂O)](NO₃) {[6](NO₃)} (Step 1)

The pH of an aqueous solution of the [5](NO₃)₂ (0.72 mmol) obtained inExample 8 was adjusted to pH 6 using a 0.01 M aqueous nitric acidsolution followed by introducing hydrogen (1 atm) into the aqueoussolution at 25° C. for 24 hours to obtain [6](NO₃).

Elementary analysis: theoretical values ([6](NO₃)); C, 42.05%; H, 4.07%;N, 22.63%; measured values; C, 42.18%; H, 3.99%; N, 22.47%.

Example 10 Synthesis of [Cr^(II) ₂(iMP)₂(H₂O)₄](NO₃)₄ {[7](NO₃)₄} (Step2)

Sodium nitrate (0.52 mmol) was added to a suspended aqueous solution ofthe [6](NO₃) (0.51 mmol) obtained in Example 9 followed by introducingoxygen (1 atm) for 3 hours at 25° C. to obtain a solution and passingthe resulting solution through Sephadex and removing the solvent underreduced pressure to obtain [7](NO₃)₄.

Elementary analysis: theoretical values ([7](NO₃)₄); C, 34.60%; H,3.80%; N, 21.72%; measured values; C, 34.67%; H, 3.89%; N, 21.66%.

Example 11 Synthesis of [Cr^(III) ₂(iMP)₂(H₂O)₄(μ-η¹:η¹-O₂)(NO₃)₄{[8](NO₃)₄} (Step 3)

Oxygen (1 atm) was passed through an aqueous solution of the [7](NO₃)₄(0.25 mmol) obtained in Example 10 for 3 hours at 25° C. followed byremoving the solvent under reduced pressure to obtain [8](NO₃)₄.

Elementary analysis: theoretical values ([8](NO₃)₄); C, 33.41%; H,3.67%; N, 20.98%; measured values; C, 33.25%; H, 3.54%; N, 21.11%.

Example 12 Release of Hydrogen Peroxide (Step 4) and Detection

Nitric acid was added to an aqueous solution of the [8](NO₃)₄ (0.24mmol) obtained in Example 11 at 25° C. followed by reacting for 3 hoursand releasing hydrogen peroxide. Quantitative determination was carriedout using a titanium complex and the yield of hydrogen peroxide was 1%.

Example 13 Synthesis of [Mn^(III)(iMP)Cl₃]

Mn^(III)Cl₃ (2.0 mmol) and iMP (2.1 mmol) were mixed in ethanol toobtain [Mn^(III)(iMP)Cl₃] (Mn^(III)Cl₃ is a commercially availableproduct (manganese trichloride)).

Elementary analysis: theoretical values ([Mn^(III)(iMP)Cl₃]); C, 38.98%;H, 3.27%; N, 17.48%; measured values; C, 38.77%; H, 3.08%; N, 17.54%.

Example 14 Synthesis of [Mn^(III)(iMP)(OH)(H₂O)₂](NO₃)₂ {[9](NO₃)₂}

AgNO₃ (3.0 mmol) was added to the [Mn^(III)(iMP)Cl₃] (1.0 mmol) obtainedin Example 13 in water (temperature: 25° C.) followed by precipitationof AgCl. AgCl was removed by filtering the reaction solution followed byremoving the water from the filtrate under reduced pressure to obtain[9](NO₃)₂.

Elementary analysis: theoretical values ([9](NO₃)₂); C, 33.13%; H,3.85%; N, 20.81%; measured values; C, 33.25%; H, 4.02%; N, 20.63%.

Example 15 Synthesis of [Mn^(I)(iMP)(H₂O)](NO₃) {[10](NO₃)} (Step 1)

The pH of an aqueous solution of the [9](NO₃)₂ (0.88 mmol) obtained inExample 14 was adjusted to pH 6 using a 0.01 M aqueous nitric acidsolution followed by introducing hydrogen (1 atm) into the aqueoussolution at 25° C. for 24 hours and allowing to react to obtain[10](NO₃).

Elementary analysis: theoretical values ([10](NO₃)); C, 41.72%; H,4.04%; N, 22.46%; measured values; C, 41.80%; H, 4.18%; N, 22.55%.

Example 16 Synthesis of [Mn^(II) ₂(iMP)₂(H₂O)₄](NO₃)₄ {[11](NO₃)₄} (Step2)

Sodium nitrate (0.56 mmol) was added to a suspended aqueous solution ofthe [10](NO₃) (0.55 mmol) obtained in Example 15 followed by introducingoxygen (1 atm) for 3 hours at 25° C., passing the resulting solutionthrough Sephadex and removing the solvent under reduced pressure toobtain [11](NO₃)₄.

Elementary analysis: theoretical values ([11](NO₃)₄); C, 34.37%; H,3.77%; N, 21.58%; measured values; C, 34.58%; H, 3.91%; N, 21.48%.

Example 17 Synthesis of [Mn^(III) ₂(iMP)₂(H₂O)₄(μ-η¹:η¹-O₂)](NO₃)₄{[12](NO₃)₄} (Step 3)

Oxygen (1 atm) was passed through an aqueous solution of the{[11](NO₃)₄} (0.22 mmol) obtained in Example 16 for 3 hours at 25° C.after which the solution changed to a reddish-brown solution. Thesolvent was removed under reduced pressure to obtain a reddish-brownsolid.

Elementary analysis: theoretical values ([12](NO₃)₄); C, 33.20%; H,3.64%; N, 20.85%; measured values; C, 33.08%; H, 3.51%; N, 21.07%.

Example 18 Release of Hydrogen Peroxide (Step 4) and Detection

Nitric acid was added to an aqueous solution of the [12](NO₃)₄ (0.21mmol) obtained in Example 17 at 25° C. followed by reacting for 3 hoursand releasing hydrogen peroxide. Quantitative determination was carriedout using a titanium complex and the yield of hydrogen peroxide was 1%.

Example 19 Synthesis of [Fe^(III)(iMP)Cl₃]

Fe^(III)Cl₃ (2.0 mmol) and iMP (2.1 mmol) were mixed in ethanol toobtain [Fe^(III)(iMP)Cl₃] (Fe^(III)Cl₃ is a commercially availableproduct (iron trichloride)).

Elementary analysis: theoretical values ([Fe^(III)(iMP)Cl₃]); C, 38.89%;H, 3.26%; N, 17.44%; measured values; C, 38.77%; H, 3.09%; N, 17.21%.

Example 20 Synthesis of [Fe^(III)(iMP)(OH)(H₂O)₂](NO₃)₂ {[13](NO₃)₂}

AgNO₃ (3.0 mmol) was added to the [Fe^(III)(iMP)Cl₃] (1.0 mmol) obtainedin Example 19 in water (temperature: 25° C.) followed by precipitationof AgCl. AgCl was removed by filtering the reaction solution followed byremoving the water from the filtrate under reduced pressure to obtain[13](NO₃)₂.

Elementary analysis: theoretical values ([13](NO₃)₂); C, 33.07%; H,3.84%; N, 20.77%; measured values; C, 32.98%; H, 4.01%; N, 20.60%.

Example 21 Synthesis of [Fe^(I)(iMP)(H₂O)](NO₃)([14](NO₃)) (Step 1)

The pH of an aqueous solution of the [13](NO₃)₂ (0.90 mmol) obtained inExample 20 was adjusted to pH 6 using a 0.01 M aqueous nitric acidsolution followed by introducing hydrogen (1 atm) into the aqueoussolution at 25° C. for 24 hours and allowing to react to obtain[14](NO₃).

Elementary analysis: theoretical values ([14](NO₃)); C, 41.62%; H,4.03%; N, 22.40%; measured values; C, 41.54%; H, 3.97%; N, 22.27%.

Example 22 Synthesis of [Fe^(II) ₂(iMP)₂(H₂O)₄](NO₃)₄ {[15](NO₃)₄} (Step2)

Sodium nitrate (0.72 mmol) was added to a suspended aqueous solution ofthe [14](NO₃) (0.71 mmol) obtained in Example 21 followed by introducingoxygen (1 atm) for 3 hours at 25° C., passing the resulting solutionthrough Sephadex and removing the solvent under reduced pressure toobtain [15](NO₃)₄.

Elementary analysis: theoretical values ([15](NO₃)₄); C, 34.30%; H,3.76%; N, 21.54%; measured values; C, 34.17%; H, 3.58%; N, 21.56%.

Example 23 Synthesis of [Fe^(III) ₂(iMP)₂(H₂O)₄(μ-η¹:η¹-O₂)](NO₃)₄{[16](NO₃)₄} (Step 3)

Oxygen (1 atm) was passed through an aqueous solution of the{[15](NO₃)₄} (0.35 mmol) obtained in Example 22 for 3 hours at 25° C.followed by removing the solvent under reduced pressure to obtain[16](NO₃)₄.

Elementary analysis: theoretical values ([16](NO₃)₄); C, 33.14%; H,3.64%; N, 20.81%; measured values; C, 33.31%; H, 3.78%; N, 20.66%.

Example 24 Release of Hydrogen Peroxide (Step 4) and Detection

Nitric acid was added to an aqueous solution of the [16](NO₃)₄ (0.34mmol) obtained in Example 23 at 25° C. followed by reacting for 3 hoursand releasing hydrogen peroxide. Quantitative determination was carriedout using a titanium complex and the yield of hydrogen peroxide was 1%.

Example 25 Synthesis of [Co^(III)(iMP)Cl₃]

Co^(III)Cl₃ (2.0 mmol) and iMP (2.1 mmol) were mixed in ethanol toobtain [Co^(III)(iMP)Cl₃] (Co^(III)Cl₃ is a commercially availableproduct (cobalt trichloride)).

Elementary analysis: theoretical values ([Co^(III)(iMP)Cl₃]); C, 38.59%;H, 3.24%; N, 17.31%; measured values; C, 38.45%; H, 3.01%; N, 17.15%.

Example 26 Synthesis of [Co^(III)(iMP)(OH)(H₂O)₂](NO₃)₂ {[17](NO₃)₂}

AgNO₃ (3.0 mmol) was added to the [Co^(III)(iMP)Cl₃] (1.0 mmol) obtainedin Example 25 in water (temperature: 25° C.) followed by precipitationof AgCl. AgCl was removed by filtering the reaction solution followed byremoving the water from the filtrate under reduced pressure to obtain[17](NO₃)₂.

Elementary analysis: theoretical values ([17](NO₃)₂); C, 32.85%; H,3.82%; N, 20.63%; measured values; C, 32.99%; H, 3.70%; N, 20.52%.

Example 27 Synthesis of [Co^(I)(iMP)(H₂O)](NO₃) {[18](NO₃)} (Step 1)

The pH of an aqueous solution of the [17](NO₃)₂ (0.91 mmol) obtained inExample 26 was adjusted to pH 6 using a 0.01 M aqueous nitric acidsolution followed by introducing hydrogen (1 atm) into the aqueoussolution at 25° C. for 24 hours and allowing to react to obtain[18](NO₃).

Elementary analysis: theoretical values ([18](NO₃)); C, 41.28%; H,4.00%; N, 22.22%; measured values; C, 41.35%; H, 4.23%; N, 22.03%.

Example 28 Synthesis of [Co^(II) ₂(iMP)₂(H₂O)₄](NO₃)₄ {[19](NO₃)₄} (Step2)

Sodium nitrate (0.74 mmol) was added to a suspended aqueous solution ofthe [18](NO₃) (0.75 mmol) obtained in Example 27 followed by introducingoxygen (1 atm) for 3 hours at 25° C., passing the resulting solutionthrough Sephadex and removing the solvent under reduced pressure toobtain [19](NO₃)₄.

Elementary analysis: theoretical values ([19](NO₃)₄); C, 34.07%; H,3.74%; N, 21.40%; measured values; C, 34.21%; H, 3.80%; N, 21.29%.

Example 29 Synthesis of [Co^(III) ₂(iMP)₂(H₂O)₄(α-η¹:η¹-O₂)](NO₃)₄{[20](NO₃)₄} (Step 3)

Oxygen (1 atm) was passed through an aqueous solution of the [19](NO₃)₄(0.27 mmol) obtained in Example 28 for 3 hours at 25° C. followed byremoving the solvent under reduced pressure to obtain [20](NO₃)₄.

Elementary analysis: theoretical values ([20](NO₃)₄); C, 32.92%; H,3.61%; N, 20.67%; measured values; C, 32.88%; H, 3.52%; N, 20.83%.

Example 30 Release of Hydrogen Peroxide (Step 4) and Detection

Nitric acid was added to an aqueous solution of the [20](NO₃)₄ (0.26mmol) obtained in Example 29 at 25° C. followed by reacting for 3 hoursand releasing hydrogen peroxide. Quantitative determination was carriedout using a titanium complex and the yield of hydrogen peroxide was 1%.

Example 31 Synthesis of [Ni^(II)(iMP)Cl₂]

Ni^(II)Cl₂ (2.0 mmol) and iMP (2.1 mmol) were mixed in ethanol to obtain[Ni^(II)(iMP)Cl₂] (Ni^(II)Cl₂ is a commercially available product(nickel dichloride)).

Elementary analysis: theoretical values ([Ni^(II)(iMP)Cl₂]): C, 42.33%;H, 3.55%; N, 18.99%; measured values: C, 42.39%; H, 3.37%; N, 19.18%.

Example 32 Synthesis of [Ni^(II)(iMP)(OH)(H₂O)₂](NO₃) {[21](NO₃)}

AgNO₃ (2.0 mmol) was added to the [Ni^(II)(iMP)Cl₂] (1.0 mmol) obtainedin Example 31 in water (temperature: 25° C.) followed by precipitationof AgCl. AgCl was removed by filtering the reaction solution followed byremoving the water from the filtrate under reduced pressure to obtain[21](NO₃).

Elementary analysis: theoretical values ([21](NO₃)); C, 37.80%; H,4.39%; N, 20.35%; measured values; C, 37.70%; H, 4.21%; N, 20.24%.

Example 33 Synthesis of [Ni⁰(iMP)(H₂O)] {[22]} (Step 1)

The pH of an aqueous solution of the [21](NO₃)(0.90 mmol) obtained inExample 32 was adjusted to pH 6 using a 0.01 M aqueous nitric acidsolution followed by introducing hydrogen (1 atm) into the aqueoussolution at 25° C. for 24 hours and allowing to react to obtain [22].

Elementary analysis: theoretical values ([22]); C, 49.41%; H, 4.78%; N,22.16%; measured values; C, 41.25%; H, 4.16%; N, 15.34%.

Example 34 Synthesis of [Ni^(I) ₂(iMP)₂(H₂O)₄](NO₃)₂ {[23](NO₃)₂} (Step2)

Sodium nitrate (0.78 mmol) was added to a suspended aqueous solution ofthe [22] (0.77 mmol) obtained in Example 33 followed by introducingoxygen (1 atm) for 3 hours at 25° C., passing the resulting solutionthrough Sephadex and removing the solvent under reduced pressure toobtain [23](NO₃)₂.

Elementary analysis: theoretical values ([23](NO₃)₂); C, 40.81%; H,5.14%; N, 20.40%; measured values; C, 40.65%; H, 4.94%; N, 20.68%.

Example 35 Synthesis of [Ni^(II) ₂(iMP)₂(H₂O)₄(μ-η¹:η¹-O₂)](NO₃)₂{[24](NO₃)₂} (Step 3)

Oxygen (1 atm) was passed through an aqueous solution of the{[23](NO₃)₂} (0.38 mmol) obtained in Example 34 for 3 hours at 25° C.followed by removing the solvent from the resulting solution underreduced pressure to obtain [24](NO₃)₂.

Elementary analysis: theoretical values ([24](NO₃)₂); C, 37.90%; H,4.16%; N, 20.40%; measured values; C, 37.79%; H, 4.22%; N, 20.60%.

Example 36 Release of Hydrogen Peroxide (Step 4) and Detection

Nitric acid was added to an aqueous solution of the [24](NO₃)₂ (0.37mmol) obtained in Example 35 at 25° C. followed by reacting for 3 hoursand releasing hydrogen peroxide. Quantitative determination was carriedout using a titanium complex and the yield of hydrogen peroxide was 1%.

Example 37 Synthesis of [Cu^(II)(iMP)Cl₂]

Cu^(II)Cl₂ (2.0 mmol) and iMP (2.1 mmol) were mixed in ethanol to obtain[Cu^(II)(iMP)Cl₂] (Cu^(II)Cl₂ is a commercially available product(copper chloride)).

Elementary analysis: theoretical values ([Cu^(II)(iMP)Cl₂]): C, 41.78%;H, 3.51%; N, 18.74%; measured values: C, 41.61%; H, 3.35%; N, 18.98%.

Example 38 Synthesis of [Cu^(II)(iMP)(OH)(H₂O)₂](NO₃) {[25](NO₃)}

AgNO₃ (2.0 mmol) was added to the [Cu^(II)(iMP)Cl₂] (1.0 mmol) obtainedin Example 37 in water (temperature: 25° C.) followed by precipitationof AgCl. AgCl was removed by filtering the reaction solution followed byremoving the water from the filtrate under reduced pressure to obtain[25](NO₃).

Elementary analysis: theoretical values ([25](NO₃)); C, 37.37%; H,4.34%; N, 20.11%; measured values; C, 37.50%; H, 4.39%; N, 20.00%.

Example 39 Synthesis of [Cu⁰(iMP)(H₂O)] {[26]} (Step 1)

The pH of an aqueous solution of the [25](NO₃) (0.88 mmol) obtained inExample 38 was adjusted to pH 6 using a 0.01 M aqueous nitric acidsolution followed by introducing hydrogen (1 atm) into the aqueoussolution at 25° C. for 24 hours and allowing to react to obtain [26].

Elementary analysis: theoretical values ([26]); C, 48.67%; H, 4.71%; N,21.83%; measured values; C, 48.90%; H, 4.60%; N, 22.07%.

Example 40 Synthesis of [Cu^(I) ₂(iMP)₂(H₂O)₄](NO₃)₂ {[27](NO₃)₂} (Step2)

Sodium nitrate (0.67 mmol) was added to a suspended aqueous solution ofthe [26] (0.66 mmol) obtained in Example 39 followed by introducingoxygen (1 atm) for 3 hours at 25° C., passing the resulting solutionthrough Sephadex and removing the solvent under reduced pressure toobtain [27](NO₃)₂.

Elementary analysis: theoretical values ([27](NO₃)₂); C, 38.95%; H,4.27%; N, 20.97%; measured values; C, 38.71%; H, 4.55%; N, 21.06%.

Example 41 Synthesis of [Cu^(II) ₂(iMP)₂(H₂O)₄(μ-η¹:η¹-O₂)](NO₃)₂{[28](NO₃)₂} (Step 3)

Oxygen (1 atm) was passed through an aqueous solution of the [27](NO₃)₂(0.33 mmol) obtained in Example 40 for 3 hours at 25° C. followed byremoving the solvent under reduced pressure to obtain [28](NO₃)₂.

Elementary analysis: theoretical values ([28](NO₃)₂); C, 37.46%; H,4.11%; N, 20.16%; measured values; C, 37.30%; H, 4.24%; N, 20.01%.

Example 42 Release of Hydrogen Peroxide (Step 4) and Detection

Nitric acid was added to an aqueous solution of the [28](NO₃)₂ (0.32mmol) obtained in Example 41 at 25° C. followed by reacting for 3 hoursand releasing hydrogen peroxide. Quantitative determination was carriedout using a titanium complex and the yield of hydrogen peroxide was 1%.

Example 43 Synthesis of [Mo^(III)(iMP)Cl₃]

Mo^(III)Cl₃ (2.0 mmol) and iMP (2.1 mmol) were mixed in ethanol toobtain [Mo^(III)(iMP)Cl₃] (Mo^(III)Cl₃ is a commercially availableproduct (molybdenum trichloride)).

Elementary analysis: theoretical values ([Mo^(III)(iMP)Cl₃]); C, 35.36%;H, 2.97%; N, 15.86%; measured values; C, 35.11%; H, 2.79%; N, 15.65%.

Example 44 Synthesis of [Mo^(III)(iMP)(OH)(H₂O)₂](NO₃)₂ {[29](NO₃)₂}

AgNO₃ (3.0 mmol) was added to the [Mo^(III)(iMP)Cl₃] (1.0 mmol) obtainedin Example 43 in water (temperature: 25° C.) followed by precipitationof AgCl. AgCl was removed by filtering the reaction solution followed byremoving the water from the filtrate under reduced pressure to obtain[29](NO₃)₂.

Elementary analysis: theoretical values ([29](NO₃)₂); C, 30.48%; H,3.54%; N, 19.14%; measured values; C, 30.60%; H, 3.47%; N, 19.07%.

Example 45 Synthesis of [Mo^(I)(iMP)(H₂O)](NO₃) {[30](NO₃)} (Step 1)

The pH of an aqueous solution of the [29](NO₃)₂ (0.91 mmol) obtained inExample 44 was adjusted to pH 6 using a 0.01 M aqueous nitric acidsolution followed by introducing hydrogen (1 atm) into the aqueoussolution at 25° C. for 24 hours and allowing to react to obtain[30](NO₃).

Elementary analysis: theoretical values ([30](NO₃)); C, 37.60%; H,3.64%; N, 20.24%; measured values; C, 37.50%; H, 3.81%; N, 20.03%.

Example 46 Synthesis of [Mo^(II) ₂(iMP)₂(H₂O)₄](NO₃)₄ {[31](NO₃)₄} (Step2)

Sodium nitrate (0.72 mmol) was added to a suspended aqueous solution ofthe [30](NO₃) (0.71 mmol) obtained in Example 45 followed by introducingoxygen (1 atm) for 3 hours at 25° C., passing the resulting solutionthrough Sephadex and removing the solvent under reduced pressure toobtain [31](NO₃)₄.

Elementary analysis: theoretical values ([31](NO₃)₄); C, 31.53%; H,3.46%; N, 19.80%; measured values; C, 31.39%; H, 3.25%; N, 19.62%.

Example 47 Synthesis of [Mo^(III) ₂(iMP)₂(H₂O)₄(μ-η¹:η¹-O₂)(NO₃)₄{[32](NO₃)₄} (Step 3)

Oxygen (1 atm) was passed through an aqueous solution of the [31](NO₃)₄(0.35 mmol) obtained in Example 46 for 3 hours at 25° C. followed byremoving the solvent under reduced pressure to obtain [32](NO₃)₄.

Elementary analysis: theoretical values ([32](NO₃)₄); C, 30.54%; H,3.35%; N, 19.18%; measured values; C, 30.41%; H, 3.21%; N, 19.32%.

Example 48 Release of Hydrogen Peroxide (Step 4) and Detection

Nitric acid was added to an aqueous solution of the [32](NO₃)₄ (0.34mmol) obtained in Example 47 at 25° C. followed by reacting for 3 hoursand releasing hydrogen peroxide. Quantitative determination was carriedout using a titanium complex and the yield of hydrogen peroxide was 1%.

Example 49 Synthesis of [Ru^(III)(iMP)Cl₃]

Ru^(III)Cl₃ (2.0 mmol) and iMP (2.1 mmol) were heated to reflux inethanol to obtain [Ru^(III)(iMP)Cl₃] (Ru^(III)Cl₃ is a commerciallyavailable product (ruthenium trichloride)).

Elementary analysis: theoretical values ([Ru^(III)(iMP)Cl₃]); C, 34.95%;H, 2.93%; N, 15.68%; measured values; C, 34.88%; H, 2.76%; N, 15.53%.

Example 50 Synthesis of [Ru^(III)(iMP)(OH)(H₂O)₂](NO₃)₂ {[33](NO₃)₂}

AgNO₃ (3.0 mmol) was added to the [Ru^(III)(iMP)Cl₃] (1.0 mmol) obtainedin Example 49 in water followed by refluxing for 12 hours at 100° C. andprecipitation of AgCl. AgCl was removed by filtering the reactionsolution followed by removing the water from the filtrate under reducedpressure to obtain [33](NO₃)₂.

Elementary analysis: theoretical values ([33](NO₃)₂); C, 30.18%; H,3.51%; N, 18.95%; measured values; C, 30.30%; H, 3.41%; N, 18.83%.

Example 51 Synthesis of [Ru^(I)(iMP)(H₂O)](NO₃) {[34](NO₃)} (Step 1)

The pH of an aqueous solution of the [33](NO₃)₂ (0.85 mmol) obtained inExample 50 was adjusted to pH 6 using a 0.01 M aqueous nitric acidsolution followed by introducing hydrogen (1 atm) into the aqueoussolution at 25° C. for 24 hours and allowing to react to obtain[34](NO₃).

Elementary analysis: theoretical values ([34](NO₃)); C, 37.14%; H,3.60%; N, 19.99%; measured values; C, 37.01%; H, 3.77%; N, 19.86%.

Example 52 Synthesis of [Ru^(II) ₂(iMP)₂(H₂O)₄](NO₃)₄ {[35](NO₃)₄} (Step2)

Sodium nitrate (0.64 mmol) was added to a suspended aqueous solution ofthe [34](NO₃) (0.63 mmol) obtained in Example 51 followed by introducingoxygen (1 atm) for 3 hours at 25° C., passing the resulting solutionthrough Sephadex and removing the solvent under reduced pressure toobtain [35](NO₃)₄.

Elementary analysis: theoretical values ([35](NO₃)₄); C, 31.20%; H,3.42%; N, 19.59%; measured values; C, 31.04%; H, 3.21%; N, 19.43%.

Example 53 Synthesis of [Ru^(III) ₂(iMP)₂(H₂O)₄(μ-η¹:η¹-O₂)(NO₃)₄{[36](NO₃)₄} (Step 3)

Oxygen (1 atm) was passed through an aqueous solution of the [35](NO₃)₄(0.31 mmol) obtained in Example 52 for 3 hours at 25° C. followed byremoving the solvent under reduced pressure to obtain [36](NO₃)₄.

Elementary analysis: theoretical values ([36](NO₃)₄); C, 30.24%; H,3.32%; N, 18.99%; measured values; C, 30.09%; H, 3.18%; N, 19.05%.

Example 54 Release of Hydrogen Peroxide (Step 4) and Detection

Nitric acid was added to an aqueous solution of the [36](NO₃)₄ (0.30mmol) obtained in Example 53 at 25° C. followed by reacting for 3 hoursand releasing hydrogen peroxide. Quantitative determination was carriedout using a titanium complex and the yield of hydrogen peroxide was 1%.

Example 55 Synthesis of [Pd^(II)(iMP)Cl₂]

Pd^(II)Cl₂ (2.0 mmol) and iMP (2.1 mmol) were heated to reflux inethanol to obtain [Pd^(II)(iMP)Cl₂] (Pd^(II)Cl₂ is a commerciallyavailable product (palladium dichloride)).

Elementary analysis: theoretical values ([Pd^(II)(iMP)Cl₂]); C, 37.48%;H, 3.15%; N, 16.81%; measured values; C, 37.32%; H, 2.96%; N, 16.63%.

Example 56 Synthesis of [Pd^(II)(iMP)(OH)(H₂O)₂](NO₃) {[37](NO₃)}

AgNO₃ (2.0 mmol) was added to the [Pd^(II)(iMP)Cl₂] (1.0 mmol) obtainedin Example 55 in water followed by refluxing for 12 hours at 100° C. andprecipitation of AgCl. AgCl was removed by filtering the reactionsolution followed by removing the water from the filtrate under reducedpressure to obtain [37](NO₃).

Elementary analysis: theoretical values ([37](NO₃)); C, 33.89%; H,3.94%; N, 18.24%; measured values; C, 33.79%; H, 3.87%; N, 18.33%.

Example 57 Synthesis of [Pd⁰(iMP)(H₂O)] {[38]} (Step 1)

The pH of an aqueous solution of the [37](NO₃) (0.88 mmol) obtained inExample 56 was adjusted to pH 6 using a 0.01 M aqueous nitric acidsolution followed by introducing hydrogen (1 atm) into the aqueoussolution at 25° C. for 24 hours and allowing to react to obtain [38].

Elementary analysis: theoretical values ([38]); C, 42.93%; H, 4.16%; N,19.26%; measured values; C, 42.90%; H, 3.95%; N, 19.46%.

Example 58 Synthesis of [Pd^(I) ₂(iMP)₂(H₂O)₄](NO₃)₂ {[39](NO₃)₂} (Step2)

Sodium nitrate (0.72 mmol) was added to a suspended aqueous solution ofthe [38] (0.71 mmol) obtained in Example 57 followed by introducingoxygen (1 atm) for 3 hours at 25° C., passing the resulting solutionthrough Sephadex and removing the solvent under reduced pressure toobtain [39](NO₃)₂.

Elementary analysis: theoretical values ([39](NO₃)₂); C, 35.19%; H,3.86%; N, 18.94%; measured values; C, 34.99%; H, 3.75%; N, 19.16%.

Example 59 Synthesis of [Pd^(II) ₂(iMP)₂(H₂O)₄(μ-η¹:η¹-O₂)](NO₃)₂{[40](NO₃)₂} (Step 3)

Oxygen (1 atm) was passed through an aqueous solution of the [39](NO₃)₂(0.35 mmol) obtained in Example 58 for 3 hours at 25° C. followed byremoving the solvent under reduced pressure to obtain [40](NO₃)₂.

Elementary analysis: theoretical values ([40](NO₃)₂); C, 33.96%; H,3.73%; N, 18.28%; measured values; C, 33.82%; H, 3.53%; N, 18.01%.

Example 60 Release of Hydrogen Peroxide (Step 4) and Detection

Nitric acid was added to an aqueous solution of the [40](NO₃)₂ (0.34mmol) obtained in Example 59 at 25° C. followed by reacting for 3 hoursand releasing hydrogen peroxide. Quantitative determination was carriedout using a titanium complex and the yield of hydrogen peroxide was 1%.

Example 61 Synthesis of [Ag^(I)(iMP)Cl]

Ag^(I)Cl (2.0 mmol) and iMP (2.1 mmol) were heated to reflux in ethanolto obtain [Ag^(I)(iMP)Cl] (Ag^(I)Cl is a commercially available product(silver chloride)).

Elementary analysis: theoretical values ([Ag^(I)(iMP)Cl]); C, 42.18%; H,4.30%; N, 17.57%; measured values; C, 42.29%; H, 4.51%; N, 17.33%.

Example 62 Synthesis of [Ag^(I)(iMP)(OH)(H₂O)₂ ]{[41]}

AgNO₃ (1.0 mmol) was added to the [Ag^(I)(iMP)Cl] (1.0 mmol) obtained inExample 61 in water followed by refluxing for 12 hours at 100° C. andprecipitation of AgCl. AgCl was removed by filtering the reactionsolution followed by removing the water from the filtrate under reducedpressure to obtain [41].

Elementary analysis: theoretical values ([41]); C, 39.02%; H, 4.53%; N,17.50%; measured values; C, 39.16%; H, 4.73%; N, 18.05%.

Example 63 Synthesis of [Ag⁰(iMP)(H₂O)] {[42]} (Step 1)

The pH of an aqueous solution of the [41] (0.86 mmol) obtained inExample 62 was adjusted to pH 6 using a 0.01 M aqueous nitric acidsolution followed by introducing hydrogen (1 atm) into the aqueoussolution at 25° C. for 24 hours and allowing to react to obtain [42].

Elementary analysis: theoretical values ([42]); C, 42.76%; H, 4.14%; N,19.18%; measured values; C, 42.52%; H, 3.91%; N, 19.04%.

Example 64 Synthesis of [Ag^(I) ₂(iMP)₂(H₂O)₄](NO₃)₂ {[43](NO₃)₂} (Step2)

Sodium nitrate (0.56 mmol) was added to a suspended aqueous solution ofthe [42] (0.55 mmol) obtained in Example 63 followed by introducingoxygen (1 atm) for 3 hours at 25° C., passing the resulting solutionthrough Sephadex and removing the solvent under reduced pressure toobtain [43](NO₃)₂.

Elementary analysis: theoretical values ([43](NO₃)₂); C, 35.07%; H,3.85%; N, 18.88%; measured values; C, 35.26%; H, 3.66%; N, 19.01%.

Example 65 Synthesis of [Ag^(II) ₂(iMP)₂(H₂O)₄(μ-η¹:η¹-O₂)](NO₃)₂{[44](NO₃)₂} (Step 3)

Oxygen (1 atm) was passed through an aqueous solution of the [43](NO₃)₂(0.27 mmol) obtained in Example 64 for 3 hours at 25° C. followed byremoving the solvent under reduced pressure to obtain [44](NO₃)₂.

Elementary analysis: theoretical values ([44](NO₃)₂); C, 33.86%; H,3.72%; N, 18.22%; measured values; C, 33.77%; H, 3.59%; N, 18.34%.

Example 66 Release of Hydrogen Peroxide (Step 4) and Detection

Nitric acid was added to an aqueous solution of the [44](NO₃)₂ (0.26mmol) obtained in Example 65 at 25° C. followed by reacting for 3 hoursand releasing hydrogen peroxide. Quantitative determination was carriedout using a titanium complex and the yield of hydrogen peroxide was 1%.

Example 67 Synthesis of [W^(III)(iMP)Cl₃]

W^(III)Cl₃ (2.0 mmol) and iMP (2.1 mmol) were heated to reflux inethanol to obtain [W^(III)(iMP)Cl₃] (W^(III)Cl₃ is a commerciallyavailable product (tungsten trichloride)).

Elementary analysis: theoretical values ([W^(III)(iMP)Cl₃]); C, 29.49%;H, 2.47%; N, 13.23%; measured values; C, 29.61%; H, 2.44%; N, 13.13%.

Example 68 Synthesis of [W^(III)(iMP)(OH)(H₂O)₂](NO₃)₂ {[45](NO₃)₂}

AgNO₃ (3.0 mmol) was added to the [W^(III)(iMP)Cl₃] (1.0 mmol) obtainedin Example 67 in water followed by refluxing for 12 hours at 100° C. andprecipitation of AgCl. AgCl was removed by filtering the reactionsolution followed by removing the water from the filtrate under reducedpressure to obtain [45](NO₃)₂.

Elementary analysis: theoretical values ([45](NO₃)₂); C, 26.02%; H,3.02%; N, 16.34%; measured values; C, 25.92%; H, 3.21%; N, 16.18%.

Example 69 Synthesis of [W^(I)(iMP)(H₂O)](NO₃) {[46](NO₃)} (Step 1)

The pH of an aqueous solution of the [45](NO₃)₂ (0.85 mmol) obtained inExample 68 was adjusted to pH 6 using a 0.01 M aqueous nitric acidsolution followed by introducing hydrogen (1 atm) into the aqueoussolution at 25° C. for 24 hours and allowing to react to obtain[46](NO₃).

Elementary analysis: theoretical values ([46](NO₃)); C, 31.03%; H,3.00%; N, 16.70%; measured values; C, 31.15%; H, 3.13%; N, 16.64%.

Example 70 Synthesis of [W^(II) ₂(iMP)₂(H₂O)₄](NO₃)₄ {[47](NO₃)₄} (Step2)

Sodium nitrate (0.66 mmol) was added to a suspended aqueous solution ofthe [46](NO₃) (0.65 mmol) obtained in Example 69 followed by introducingoxygen (1 atm) for 3 hours at 25° C., passing the resulting solutionthrough Sephadex and removing the solvent under reduced pressure toobtain {47}(NO₃)₄.

Elementary analysis: theoretical values ([47](NO₃)₄); C, 26.77%; H,2.94%; N, 16.81%; measured values; C, 26.61%; H, 2.82%; N, 16.68%.

Example 71 Synthesis of [W^(III) ₂(iMP)₂(H₂O)₄(μ-η¹:η¹-O₂)(NO₃)₄{[48](NO₃)₄} (Step 3)

Oxygen (1 atm) was passed through an aqueous solution of the{[47](NO₃)₄} (0.32 mmol) obtained in Example 70 for 3 hours at 25° C.followed by removing the solvent under reduced pressure to obtain[48](NO₃)₄.

Elementary analysis: theoretical values ([48](NO₃)₄); C, 26.06%; H,2.86%; N, 16.36%; measured values; C, 26.21%; H, 3.01%; N, 16.12%.

Example 72 Release of Hydrogen Peroxide (Step 4) and Detection

Nitric acid was added to an aqueous solution of the [48](NO₃)₄ (0.31mmol) obtained in Example 71 at 25° C. followed by reacting for 3 hoursand releasing hydrogen peroxide. Quantitative determination was carriedout using a titanium complex and the yield of hydrogen peroxide was 1%.

Example 73 Synthesis of [Re^(III)(iMP)Cl₃]

Re^(III)Cl₃ (2.0 mmol) and iMP (2.1 mmol) were heated to reflux inethanol to obtain [Re^(III)(iMP)Cl₃] (Re^(III)Cl₃ is a commerciallyavailable product (rhenium trichloride)).

Elementary analysis: theoretical values ([Re^(III)(iMP)Cl₃]); C, 29.36%;H, 2.46%; N, 13.17%; measured values; C, 29.45%; H, 2.57%; N, 13.29%.

Example 74 Synthesis of [Re^(III)(iMP)(OH)(H₂O)₂](NO₃)₂ {[49](NO₃)₂}

AgNO₃ (3.0 mmol) was added to the [Re^(III)(iMP)Cl₃] (1.0 mmol) obtainedin Example 73 in water followed by refluxing for 12 hours at 100° C. andprecipitation of AgCl. AgCl was removed by filtering the reactionsolution followed by removing the water from the filtrate under reducedpressure to obtain [49](NO₃)₂.

Elementary analysis: theoretical values ([49](NO₃)₂); C, 25.91%; H,3.01%; N, 16.27%; measured values; C, 25.99%; H, 3.23%; N, 16.06%.

Example 75 Synthesis of [Re^(I)(iMP)(H₂O)](NO₃) {[50](NO₃)} (Step 1)

The pH of an aqueous solution of the [49](NO₃)₂ (0.81 mmol) obtained inExample 74 was adjusted to pH 6 using a 0.01 M aqueous nitric acidsolution followed by introducing hydrogen (1 atm) into the aqueoussolution at 25° C. for 24 hours to obtain [50](NO₃).

Elementary analysis: theoretical values ([50](NO₃)); C, 30.89%; H,2.99%; N, 16.63%; measured values; C, 31.03%; H, 3.11%; N, 16.76%.

Example 76 Synthesis of [Re^(II) ₂(iMP)₂(H₂O)₄](NO₃)₄ {[51](NO₃)₄} (Step2)

Sodium nitrate (0.60 mmol) was added to a suspended aqueous solution ofthe [50](NO₃) (0.59 mmol) obtained in Example 75 followed by introducingoxygen (1 atm) for 3 hours at 25° C., passing the resulting solutionthrough Sephadex and removing the solvent under reduced pressure toobtain [51](NO₃)₄.

Elementary analysis: theoretical values ([51](NO₃)₄); C, 26.67%; H,2.93%; N, 16.75%; measured values; C, 26.53%; H, 2.75%; N, 16.58%.

Example 77 Synthesis of [Re^(III) ₂(iMP)₂(H₂O)₄(μ-η¹:η¹-O₂)](NO₃)₄{[52](NO₃)₄} (Step 3)

Oxygen (1 atm) was passed through an aqueous solution of the [51](NO₃)₄(0.29 mmol) obtained in Example 76 for 3 hours at 25° C. followed byremoving the solvent under reduced pressure to obtain [52](NO₃)₄.

Elementary analysis: theoretical values ([52](NO₃)₄); C, 25.96%; H,2.85%; N, 16.30%; measured values; C, 25.78%; H, 3.05%; N, 16.14%.

Example 78 Release of Hydrogen Peroxide (Step 4) and Detection

Nitric acid was added to an aqueous solution of the [52](NO₃)₄ (0.28mmol) obtained in Example 77 at 25° C. followed by reacting for 3 hoursand releasing hydrogen peroxide. Quantitative determination was carriedout using a titanium complex and the yield of hydrogen peroxide was 1%.

Example 79 Synthesis of [Os^(III)(iMP)Cl₃]

Os^(III)Cl₃ (2.0 mmol) and iMP (2.1 mmol) were heated to reflux inethanol to obtain [Os^(III)(iMP)Cl₃] (Os^(III)Cl₃ is a commerciallyavailable product (osmium trichloride)).

Elementary analysis: theoretical values ([Os^(III)(iMP)Cl₃]); C, 29.14%;H, 2.45%; N, 13.07%; measured values; C, 29.35%; H, 2.42%; N, 13.01%.

Example 80 Synthesis of [Os^(III)(iMP)(OH)(H₂O)₂](NO₃)₂ {[53](NO₃)₂}

AgNO₃ (3.0 mmol) was added to the [Os^(III)(iMP)Cl₃] (1.0 mmol) obtainedin Example 79 in water followed by refluxing for 12 hours at 100° C. andprecipitation of AgCl. AgCl was removed by filtering the reactionsolution followed by removing the water from the filtrate under reducedpressure to obtain [53](NO₃)₂.

Elementary analysis: theoretical values ([53](NO₃)₂); C, 25.74%; H,2.99%; N, 16.16%; measured values; C, 25.78%; H, 3.05%; N, 15.98%.

Example 81 Synthesis of [Os^(I)(iMP)(H₂O)](NO₃) {[54](NO₃)} (Step 1)

The pH of an aqueous solution of the [53](NO₃)₂ (0.84 mmol) obtained inExample 80 was adjusted to pH 6 using a 0.01 M aqueous nitric acidsolution followed by introducing hydrogen (1 atm) into the aqueoussolution at 25° C. for 24 hours and allowing to react to obtain[54](NO₃).

Elementary analysis: theoretical values ([54](NO₃)); C, 30.64%; H,2.97%; N, 16.49%; measured values; C, 30.54%; H, 2.89%; N, 16.35%.

Example 82 Synthesis of [Os^(II) ₂(iMP)₂(H₂O)₄](NO₃)₄ {[55](NO₃)₄} (Step2)

Sodium nitrate (0.69 mmol) was added to a suspended aqueous solution ofthe [54](NO₃) (0.68 mmol) obtained in Example 81 followed by introducingoxygen (1 atm) for 3 hours at 25° C., passing the resulting solutionthrough Sephadex and removing the solvent under reduced pressure toobtain [55](NO₃)₄.

Elementary analysis: theoretical values ([55](NO₃)₄); C, 26.48%; H,2.91%; N, 16.63%; measured values; C, 26.35%; H, 2.83%; N, 16.48%.

Example 83 Synthesis of [Os^(III) ₂(iMP)₂(H₂O)₄(μ-η¹:η¹-O₂)](NO₃)₄{[56](NO₃)₄} (Step 3)

Oxygen (1 atm) was passed through an aqueous solution of the [55](NO₃)₄(0.34 mmol) obtained in Example 82 for 3 hours at 25° C. followed byremoving the solvent under reduced pressure to obtain [56](NO₃)₄.

Elementary analysis: theoretical values ([56](NO₃)₄); C, 25.78%; H,2.83%; N, 16.19%; measured values; C, 25.56%; H, 3.00%; N, 16.02%.

Example 84 Release of Hydrogen Peroxide (Step 4) and Detection

Nitric acid was added to an aqueous solution of the [56](NO₃)₄ (0.33mmol) obtained in Example 83 at 25° C. followed by reacting for 3 hoursand releasing hydrogen peroxide. Quantitative determination was carriedout using a titanium complex and the yield of hydrogen peroxide was 1%.

Example 85 Synthesis of [Ir^(III)(iMP)Cl₃]

Ir^(III)Cl₃.3H₂O (2.0 mmol) and iMP (2.1 mmol) were heated to reflux inethanol to obtain [Ir^(III)(iMP)Cl₃] (Ir^(III)Cl₃ is a commerciallyavailable product (iridium trichloride)).

Elementary analysis: theoretical values ([Ir^(III)(iMP)Cl₃]); C, 29.03%;H, 2.44%; (N, 13.02%; measured values; C, 29.29%; H, 2.55%; N, 13.12%.

Example 86 Synthesis of [Ir^(III)(iMP)(OH)(H₂O)₂](NO₃)₂ {[57](NO₃)₂}

AgNO₃ (3.0 mmol) was added to the [Ir^(III)(iMP)Cl₃] (1.0 mmol) obtainedin Example 85 in water followed by refluxing for 12 hours at 100° C. andprecipitation of AgCl. AgCl was removed by filtering the reactionsolution followed by removing the water from the filtrate under reducedpressure to obtain [57](NO₃)₂.

Elementary analysis: theoretical values ([57](NO₃)₂); C, 25.66%; H,2.98%; N, 16.11%; measured values; C, 25.77%; H, 3.13%; N, 16.24%.

Example 87 Synthesis of [Ir^(I)(iMP)(H₂O)](NO₃) {[58](NO₃)} (Step 1)

The pH of an aqueous solution of the [57](NO₃)₂ (0.80 mmol) obtained inExample 86 was adjusted to pH 6 using a 0.01 M aqueous nitric acidsolution followed by introducing hydrogen (1 atm) into the aqueoussolution at 25° C. for 24 hours and allowing to react to obtain[58](NO₃).

Elementary analysis: theoretical values ([58](NO₃)); C, 30.52%; H,2.96%; N, 16.43%; measured values; C, 30.42%; H, 3.16%; N, 16.29%.

Example 88 Synthesis of [Ir^(II) ₂(iMP)₂(H₂O)₄](NO₃)₄ {[59](NO₃)₄} (Step2)

Sodium nitrate (0.59 mmol) was added to a suspended aqueous solution ofthe [58](NO₃) (0.58 mmol) obtained in Example 87 followed by introducingoxygen (1 atm) for 3 hours at 25° C., passing the resulting solutionthrough Sephadex and removing the solvent under reduced pressure toobtain [59](NO₃)₄.

Elementary analysis: theoretical values ([59](NO₃)₄); C, 26.48%; H,2.91%; N, 16.63%; measured values; C, 26.35%; H, 2.83%; N, 16.48%.

Example 89 Synthesis of [Ir^(III) ₂(iMP)₂(H₂O)₄(μ-η¹:η¹-O₂)(NO₃)₄{[60](NO₃)₄} (Step 3)

Oxygen (1 atm) was passed through an aqueous solution of the [59](NO₃)₄(0.29 mmol) obtained in Example 88 for 3 hours at 25° C. followed byremoving the solvent under reduced pressure to obtain [60](NO₃)₄.

Elementary analysis: theoretical values ([60](NO₃)₄); C, 25.70%; H,2.82%; N, 16.14%; measured values; C, 25.91%; H, 2.90%; N, 15.97%.

Example 90 Release of Hydrogen Peroxide (Step 4) and Detection

Nitric acid was added to an aqueous solution of the [60](NO₃)₄ (0.28mmol) obtained in Example 89 at 25° C. followed by reacting for 3 hoursand releasing hydrogen peroxide. Quantitative determination was carriedout using a titanium complex and the yield of hydrogen peroxide was 1%.

Example 91 Synthesis of [Pt^(II)(iMP)Cl₂]

Pt^(II)Cl₂ (2.0 mmol) and iMP (2.1 mmol) were heated to reflux inethanol to obtain [Pt^(II)(iMP)Cl₂] (Pt^(II)Cl₂ is a commerciallyavailable product (platinum dichloride)).

Elementary analysis: theoretical values ([Pt^(II)(iMP)Cl₂]); C, 30.90%;H, 2.59%; N, 13.86%; measured values; C, 31.02%; H, 2.49%; N, 13.76%.

Example 92 Synthesis of [Pt^(II)(iMP)(OH)(H₂O)₂](NO₃) {[61](NO₃)}

AgNO₃ (2.0 mmol) was added to the [Pt^(II)(iMP)Cl₂] (1.0 mmol) obtainedin Example 91 in water followed by refluxing for 12 hours at 100° C. andprecipitation of AgCl. AgCl was removed by filtering the reactionsolution followed by removing the water from the filtrate under reducedpressure to obtain [61](NO₃).

Elementary analysis: theoretical values ([61](NO₃)); C, 28.42%; H,3.30%; N, 15.30%; measured values; C, 28.53%; H, 3.44%; N, 15.43%.

Example 93 Synthesis of [Pt⁰(iMP)(H₂O)] {[62]} (Step 1)

The pH of an aqueous solution of the [61](NO₃) (0.86 mmol) obtained inExample 92 was adjusted to pH 6 using a 0.01 M aqueous nitric acidsolution followed by introducing hydrogen (1 atm) into the aqueoussolution at 25° C. for 24 hours and allowing to react to obtain [62].

Elementary analysis: theoretical values ([62]); C, 34.52%; H, 3.34%; N,15.48%; measured values; C, 34.48%; H, 3.47%; N, 15.23%.

Example 94 Synthesis of [Pt^(I) ₂(iMP)₂(H₂O)₄](NO₃)₂ {[63](NO₃)₂} (Step2)

Sodium nitrate (0.61 mmol) was added to a suspended aqueous solution ofthe [62] (0.60 mmol) obtained in Example 93 followed by introducingoxygen (1 atm) for 3 hours at 25° C., passing the resulting solutionthrough Sephadex and removing the solvent under reduced pressure toobtain [63](NO₃)₂.

Elementary analysis: theoretical values ([63](NO₃)₂); C, 29.33%; H,3.22%; N, 15.79%; measured values; C, 26.13%; H, 2.68%; N, 16.31%.

Example 95 Synthesis of [Pt^(II) ₂(iMP)₂(H₂O)₄(μ-η¹:η¹-O₂)(NO₃)₂{[64](NO₃)₂} (Step 3)

Oxygen (1 atm) was passed through an aqueous solution of the [63](NO₃)₂(0.30 mmol) obtained in Example 94 for 3 hours at 25° C. followed byremoving the solvent under reduced pressure to obtain [64](NO₃)₂.

Elementary analysis: theoretical values ([64](NO₃)₂); C, 28.47%; H,3.12%; N, 15.32%; measured values; C, 28.43%; H, 2.93%; N, 15.43%.

Example 96 Release of Hydrogen Peroxide (Step 4) and Detection

Nitric acid was added to an aqueous solution of the [64](NO₃)₂ (0.29mmol) obtained in Example 95 at 25° C. followed by reacting for 3 hoursand releasing hydrogen peroxide. Quantitative determination was carriedout using a titanium complex and the yield of hydrogen peroxide was 1%.

Example 97 Synthesis of [Au^(III)(iMP)Cl₃]

Au^(III)Cl₃ (2.0 mmol) and iMP (2.1 mmol) were heated to reflux inethanol to obtain [Au^(III)(iMP)Cl₃](Au^(III)Cl₃ is a commerciallyavailable product (gold trichloride)).

Elementary analysis: theoretical values ([Au^(III)(iMP)Cl₃]): C, 28.78%;H, 2.41%; N, 12.91%; measured values: C, 28.97%; H, 2.51%; N, 12.77%.

Example 98 Synthesis of [Au^(III)(iMP)(OH)(H₂O)₂](NO₃)₂ {[65](NO₃)₂}

AgNO₃ (3.0 mmol) was added to the [Au^(III)(iMP)Cl₃] (1.0 mmol) obtainedin Example 97 in water followed by refluxing for 12 hours at 100° C. andprecipitation of AgCl. AgCl was removed by filtering the reactionsolution followed by removing the water from the filtrate under reducedpressure to obtain [65](NO₃)₂.

Elementary analysis: theoretical values ([65](NO₃)₂); C, 25.46%; H,2.96%; N, 15.99%; measured values; C, 25.26%; H, 3.17%; N, 16.01%.

Example 99 Synthesis of [Au^(I)(iMP)(H₂O)](NO₃) {[66](NO₃)} (Step 1)

The pH of an aqueous solution of the [65](NO₃)₂ (0.84 mmol) obtained inExample 98 was adjusted to pH 6 using a 0.01 M aqueous nitric acidsolution followed by introducing hydrogen (1 atm) into the aqueoussolution at 25° C. for 24 hours and allowing to react to obtain[66](NO₃).

Elementary analysis: theoretical values ([66](NO₃)); C, 30.24%; H,2.93%; N, 16.28%; measured values; C, 30.11%; H, 2.82%; N, 16.03%.

Example 100 Synthesis of [Au^(II) ₂(iMP)₂(H₂O)₄](NO₃)₄ {[67](NO₃)₄}(Step 2)

Sodium nitrate (0.58 mmol) was added to a suspended aqueous solution ofthe [66](NO₃) (0.57 mmol) obtained in Example 99 followed by introducingoxygen (1 atm) for 3 hours at 25° C., passing the resulting solutionthrough Sephadex and removing the solvent under reduced pressure toobtain [67](NO₃)₄.

Elementary analysis: theoretical values ([67](NO₃)₄); C, 26.19%; H,2.87%; N, 16.44%; measured values; C, 26.01%; H, 2.91%; N, 16.57%.

Example 101 Synthesis of [Au^(III) ₂(iMP)₂(H₂O)₄(μ-η¹:η¹-O₂)(NO₃)₄{[68](NO₃)₄} (Step 3)

Oxygen (1 atm) was passed through an aqueous solution of the [67](NO₃)₄(0.28 mmol) obtained in Example 100 for 3 hours at 25° C. followed byremoving the solvent under reduced pressure to obtain [68](NO₃)₄.

Elementary analysis: theoretical values ([68](NO₃)₄); C, 25.50%; H,2.80%; N, 16.01%; measured values; C, 25.64%; H, 2.73%; N, 15.91%.

Example 102 Release of Hydrogen Peroxide (Step 4) and Detection

Nitric acid was added to an aqueous solution of the [68](NO₃)₄ (0.27mmol) obtained in Example 101 at 25° C. followed by reacting for 3 hoursand releasing hydrogen peroxide. Quantitative determination was carriedout using a titanium complex and the yield of hydrogen peroxide was 1%.

The invention claimed is:
 1. A metal complex represented by a formula(1):

wherein M represents chromium, manganese, iron, cobalt, nickel, copper,molybdenum, ruthenium, rhodium, palladium, silver, tungsten, rhenium,osmium, iridium, platinum or gold, n+ represents a charge of M, R¹, R²,R⁴, R⁵, R⁶, R⁸ and R⁹ represents hydrogen atoms, R³ and R⁷ representmethyl groups, one of X, Y and Z represents OH⁻, the remaining tworepresents H₂O, m+ represents +1, An1 represents a nitrate ion, and m−represents −1 the charge of An1.
 2. A method for producing hydrogenperoxide, comprising: forming hydrogen peroxide from hydrogen and oxygenin the presence of the metal complex according to claim 1.